I suspect there's compensation/"excess space" for wear over time, somewhat like spare blocks on SSDs, and when it was new, it would've had even better range if it didn't have that compensation.
That is such a lovely thing for a big company to do in this day and age. It probably also allows them to use the battery optimally, i.e. not fully charge or discharge, for a longer lasting battery.
Chevy Volt has one of the best batteries among all EVs with excellent thermal control system. In Ukraine it is common these day to buy damaged EVs from US and restore them to brand-new state, including Tesla, Nissan Leaf and Chevy Volt. One of the shops has a Youtube channel and they made an episode comparing batteries from different cars. Chevy Volt's battery cell survived already about 3000 cycles without noticible loss of charge, the test is being running for years already, charging-discharging it every 30 minutes.